With the recent progress in integration of semiconductor devices, there has been a demand for exposure techniques capable of forming finer patterns, and development of new exposure techniques is therefore in progress. Light exposure techniques now in use include one which employs light from an ArF light source. However, the light from the ArF light source has a long wavelength and therefore has a difficulty in forming patterns with a line width equal to or below 20 nm even when various resolution improvement techniques are used in combination.
An exposure technique using a charged particle beam including an electron beam has an essential advantage that its resolution is high because a diffracted wavelength of the charged particle beam is extremely short. On the other hand, the exposure technique using the charged particle beam faces a problem of how to improve its processing speed.
Given this situation, there has been proposed complementary lithography which utilizes the light exposure technique and the charged particle beam exposure technique in a complementary manner.
In the complementary lithography, simple line-and-space patterns are produced by using the light exposure. Line-and-space patterns with a line width equal to or below 10 nm can be formed by the light exposure while using a resolution improvement technique such as double patterning in combination therewith.
Subsequently, exposure for forming cut patterns to cut the line patterns and forming via-hole patterns to connect line patterns to other line patterns on a different layer is performed by the charged particle beam exposure.
In the complementary lithography, the area of a resist pattern for performing the exposure using the charged particle beam is limited to about several percent of the area of the entire pattern. For this reason, the complementary lithography requires a significantly smaller amount of charged particle beam irradiation per wafer as compared to the case of subjecting the entire region of the pattern to the exposure by using the charged particle beam only.
Accordingly, the complementary lithography has a potential to dramatically improve a processing speed while taking advantage of the high resolution to available from the charged particle beam exposure.
Another possible option is to use a plurality of charged particle beams in order to perform efficient exposure for forming the cut patterns and the via-hole patterns on the line patterns.
Nonetheless, there is no known method of efficiently performing the exposure for forming the cut patterns and the via-hole patterns laid out on arbitrary positions on the line patterns.
The above noted conventional technologies are described in, for example, U.S. Pat. No. 7,276,714 and Japanese Laid-open Patent Publication No. 2013-093567.